1. Field of the Invention
The present invention relates to a liquid fuel cell device and liquid fuel tanks employed therein, and more specifically to a liquid fuel cell device capable of generating electrical power for a longer period of time even when it is made compact.
2. Description of the Related Art
Recently, fuel cells are becoming a focus of attention, since they have high efficiencies as single power generator devices. The fuel cells are mainly categorized into two types: a gas fuel cell in which a gas is used as the fuel, such as a phosphoric acid fuel cell, a molten carbonate fuel cell, a polymer electrolyte fuel cell and an alkaline electrolyte fuel cell; and a liquid fuel cell in which a liquid is used as the fuel, such as a methanol liquid fuel cell and a hydrazine liquid fuel cell. These fuel cells are designed mainly as a power source for driving an electrical power generator, and a large-scale device. Thus, it is necessary to employ a compressor, a pump or the like, for introducing the gas or liquid fuel and the oxidizer gas into the cell. However, in the case of fuel cells that use liquid fuels as their fuels, a useful type of such devices is that a liquid fuel is introduced into the cell by the capillary force and a fuel vaporizing section that vaporizes the liquid fuel in the cell is provided as a separate unit in order to improve the reaction rate (see Jpn. Pat. Appln. KOKAI Publication No. 10-278759, for example.)
Meanwhile, the recent trend of our society indicates that various devices such as audio devices and radio devices are downsized as the technology in the filed of semiconductor develops, and there is an increasing demand of devices of a higher portability. As the power source that can meet these demands, a simple primary battery or secondary battery is known, for example. However, in terms of functionality, primary or secondary batteries have limited time of use, and naturally, the time of use of an OA device that operates on such a battery is limited. In the case where one of these batteries is used, if the battery has completely discharged, the OA device can still be operated by replacing it. However, with a primary battery, the time of use is short for its weight, and therefore it is not suitable for a portable device. On the other hand, in the case of a secondary battery, it has an advantage of being rechargeable once it completely discharged, but at the same time, it requires a power source for charging, and therefore the location of its use is limited. In addition, the second battery entails another disadvantage of requiring a long time to recharge it. In particular, in an OA device or the like in which a secondary battery is installed, it is not easy to replace the battery when the battery has completely discharged, and therefore the usable time of the device is very much limited. As described, it is difficult, with the techniques of the conventional primary or secondary batteries, to operate various types of small-sized devices for a long period of time. Therefore, there is a strong demand for a battery or cell that is suitable for a long time operation.
As a solution for such a problem, there has been proposed liquid fuel cells described above. The liquid fuel cells have not only an advantage that they can generate electricity only by supplying a liquid fuel and an oxidizer, but also an advantage that they can generate electricity continuously if the liquid fuel is replaced. Thus, if they can be reduced in size, the liquid fuel cells can become an extremely advantageous system for small-sized devices including OA devices, which have a low consumption power.
However, when the liquid fuel cells are to be downsized, providing portability, various types of accessory device, especially, the liquid fuel supply system including a liquid fuel tank for supplying a liquid fuel to the liquid fuel cell must be reduced also in size. If the liquid fuel supply system, especially, its liquid fuel tank, is made small, the time for the cell to be able to continuously generate electricity is naturally shortened since the supply of the liquid fuel from one liquid fuel tank is shortened. Therefore, it is necessary to replace the liquid fuel tank frequently.
Further, some of the fuel cells of the type that supplies the liquid fuel use driving devices including a gear, which is used to supply a liquid fuel into the liquid fuel tank from outside. In these fuel cells, it is necessary to provide a liquid sealing at the connection portion of the tank with the outside device. In addition, due to deterioration over time, the leakage of the liquid occurs at the connection in some cases, making it impossible to obtain a stable output.